The invention concerns a coil. A coil is formed by at least one winding of an electric conductor. The electric conductor can be wound up on a coil body, which does not affect the properties of the coil and thus consists for example of plastic. The coil can comprise a core, around which the electric conductor is wound one or several times. The core changes the properties of the coil, namely in particular the inductance and quality. The both ends of the electric conductors form the both terminals of the coil.
As electric conductor is used for example a wire or a braid. A braid consists of a multiplicity of for example parallel running single wires. The single wires can run spirally, that is to say in a shape of a helix.
In order to allow measuring electromagnetic signals, a therefore suitable measuring device comprises an electric oscillating circuit (resonant circuit). An oscillating circuit comprises a coil and a capacitance. In order to obtain an oscillating circuit with low damping, coils with high quality are needed among others. The quality of a coil is the product of the measurement frequency and the ratio of inductance to resistance.
A coil with a wound electric conductor, whose ends form the both electric terminals of the coil, is known from the U.S. Pat. No. 512,340.
Besides a coil with an electric conductor and two electric terminals there are components in the field of power supply and transformators with a plurality of wound together electric conductors with a plurality of electric terminals (U.S. Pat. No. 5,640,314). Electric conductors of such components with at least four electric terminals can be twisted (RF Circuit Design, 2nd Edition, Christopher Bowick, ISBN 978-0750685184).
It is object of the invention to provide a coil with advantageous properties for an oscillating circuit, in particular for a measuring device for electromagnetic signals.
The problem of the invention is solved by means of a coil with the features of the claim 1. Advantageous embodiments result from the dependent claims.